package com.startx.http.system.encrypt.aes;

import java.security.NoSuchAlgorithmException;
import java.security.SecureRandom;

import javax.crypto.Cipher;
import javax.crypto.KeyGenerator;
import javax.crypto.SecretKey;
import javax.crypto.spec.SecretKeySpec;

import com.startx.http.system.encrypt.base64.Base64;

public class AES {

	private static final String KEY_ALGORITHM = "AES";
	private static final String DEFAULT_CIPHER_ALGORITHM = "AES/ECB/PKCS5Padding";// 默认的加密算法

	/**
	 * AES 加密操作
	 * @param content 待加密内容
	 * @param password 加密密码
	 * @return 返回Base64转码后的加密数据
	 */
	public static String encrypt(String byteContent, String password) {
		try {
			Cipher cipher = Cipher.getInstance(DEFAULT_CIPHER_ALGORITHM);// 创建密码器

			cipher.init(Cipher.ENCRYPT_MODE, getSecretKey(password));// 初始化为加密模式的密码器

			byte[] result = cipher.doFinal(byteContent.getBytes("UTF-8"));// 加密

			return Base64.encode(result);// 通过Base64转码返回
		} catch (Exception e) {
			e.printStackTrace();
		}

		return "";
	}
	
	/**
	 * AES 解密操作
	 * @param content
	 * @param password
	 * @return
	 */
	public static String decrypt(String content, String password) {

		try {
			// 实例化
			Cipher cipher = Cipher.getInstance(DEFAULT_CIPHER_ALGORITHM);

			// 使用密钥初始化，设置为解密模式
			cipher.init(Cipher.DECRYPT_MODE, getSecretKey(password));

			// 执行操作
			byte[] result = cipher.doFinal(Base64.decode(content));

			return new String(result, "utf-8");
		} catch (Exception e) {
			e.printStackTrace();
		}

		return null;
	}

	/**
	 * 生成加密秘钥
	 * @return
	 */
	private static SecretKeySpec getSecretKey(final String password) {
		// 返回生成指定算法密钥生成器的 KeyGenerator 对象
		KeyGenerator kg = null;

		try {
			kg = KeyGenerator.getInstance(KEY_ALGORITHM);

			SecureRandom random = SecureRandom.getInstance("SHA1PRNG");
	        random.setSeed(password.getBytes());
			// AES 要求密钥长度为 128
			kg.init(128, random);

			// 生成一个密钥
			SecretKey secretKey = kg.generateKey();

			return new SecretKeySpec(secretKey.getEncoded(), KEY_ALGORITHM);// 转换为AES专用密钥
		} catch (NoSuchAlgorithmException e) {
			e.printStackTrace();
		}

		return null;
	}
}
